Health: Asthma link to small families

Children from small families are significantly more likely to develop asthma than those with many brothers and sisters, research has shown. A study in Spain found that the chances of children with fewer than three older siblings getting asthma were up to three times greater then those of other youngsters. Boys were also more than twice as likely as girls to develop asthma before the age of 15, the researchers discovered. After the age of 15, girls were more likely to develop the condition.

The European Respiratory Society study, based at the Institut Municipal d'Investigacion Medica in Barcelona, examined the risk factors for asthma in 2,646 adults, aged 20 to 44, in five areas of Spain.

Dr Jordi Sunyer, who led the research, said: "These findings suggest that a child with more siblings is exposed to a greater number of environmental factors which may strengthen their immune system."